Nixpkgs currently contains:
- the linux kernel (and supporting bits+userspace to build an entire bootable OS installer/disk image/PXE payload, etc)
- tens of thousands of Linux packages (many of which also work already on Darwin, where applicable)
- thousands of native {Go,Python,Haskell,Node} dependencies
If half of the effort that has gone into Linuxbrew and other efforts like this, went into nixpkgs, it would probably have even more packages and Windows support and we could stop inventing a new package manager to rule them all every 6 months. Insert XKCD joke here.
edit: -1, zero replies, years of being here and nothing changes. gotta love it. Maybe do more research next time instead of NIH?
edit2: I'll donate $500 to the charity of your choice if you can show me a "universal package manager" that contains more packages than nixpkgs (which has existed for ages at this point). I'll wait.